JP2017090502A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device that can increase the display quality.SOLUTION: The liquid crystal display device includes: a first substrate having a first wiring, a second wiring separate from the first wiring, a first electrode, a second electrode facing the first electrode, and an interlayer insulating film between the first electrode and the second electrode; a second substrate facing the first substrate; and a liquid crystal layer containing liquid crystal molecules held between the first substrate and the second substrate, the second electrode having an edge between the first electrode and the liquid crystal layer, the edge having a first part in proximity to the first wiring, a second part in proximity to the second wiring, and a bent middle part between the first part and the second part, and the liquid crystal molecules forming a region which rotates in the same direction by an electric field between the first and second electrodes in an area between the first part and the second part.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to a liquid crystal display device.

  In recent years, horizontal electric field type liquid crystal display devices have been put into practical use. In the horizontal electric field method, the alignment state of liquid crystal molecules is controlled using an electric field formed between a pixel electrode and a common electrode provided on the same substrate. As an example of the lateral electric field method, according to Patent Document 1, at least an upper part of a pixel or a lower part of a pixel is provided with an electrode branch whose extending direction is refracted at one bending point provided above the pixel rather than the center of the pixel region. A liquid crystal panel having a pixel electrode pattern connected at the terminal end of the above is disclosed. Such a liquid crystal display device is required to improve display quality from various viewpoints.

JP 2011-164661 A

  An object of the present embodiment is to provide a liquid crystal display device capable of improving display quality.

According to this embodiment,
A first wiring; a second wiring spaced apart from the first wiring; a first electrode; a second electrode facing the first electrode; and an interlayer positioned between the first electrode and the second electrode A first substrate provided with an insulating film; a second substrate facing the first substrate; and a liquid crystal layer including liquid crystal molecules held between the first substrate and the second substrate. The second electrode has an edge located between the first electrode and the liquid crystal layer, and the edge is located on the first wiring side and on the second wiring side. And a bent intermediate portion located between the first portion and the second portion, and the liquid crystal molecule is a region between the first portion and the second portion. In the liquid crystal display device, the region rotated in the same direction by the electric field between the first electrode and the second electrode is formed. That.

FIG. 1 is a plan view showing the configuration of the liquid crystal display device of the present embodiment. FIG. 2 is a plan view showing a configuration example of one pixel PX on the first substrate SUB1 shown in FIG. FIG. 3 is a cross-sectional view of the first substrate SUB1 along the line AB in FIG. FIG. 4 is a cross-sectional view of the display panel PNL along the line CD in FIG. FIG. 5 is a diagram for explaining the operation of a liquid crystal display device to which a negative liquid crystal material is applied. FIG. 6 is a diagram for explaining the operation of a liquid crystal display device to which a positive liquid crystal material is applied. FIG. 7 is a diagram showing a simulation result of VT characteristics when a negative liquid crystal material is used. FIG. 8 is a diagram showing a simulation result of the liquid crystal response time when a negative liquid crystal material is used. FIG. 9 is a plan view showing another configuration example of one pixel PX on the first substrate SUB1 shown in FIG. FIG. 10 is a plan view showing another configuration example of one pixel PX on the first substrate SUB1 shown in FIG. FIG. 11 is a plan view showing another configuration example of one pixel PX on the first substrate SUB1 shown in FIG.

  Hereinafter, the present embodiment will be described with reference to the drawings. It should be noted that the disclosure is merely an example, and those skilled in the art can easily conceive of appropriate changes while maintaining the gist of the invention are naturally included in the scope of the present invention. In addition, for the sake of clarity, the drawings may be schematically represented with respect to the width, thickness, shape, etc. of each part as compared to actual aspects, but are merely examples, and The interpretation is not limited. In addition, in the present specification and each drawing, components that perform the same or similar functions as those described above with reference to the previous drawings are denoted by the same reference numerals, and repeated detailed description may be omitted as appropriate. .

FIG. 1 is a plan view showing the configuration of the liquid crystal display device of the present embodiment.
That is, the display panel PNL constituting the liquid crystal display device includes a first substrate SUB1, a second substrate SUB2 facing the first substrate SUB1, and a liquid crystal layer held between the first substrate SUB1 and the second substrate SUB2. LC. The first substrate SUB1 and the second substrate SUB2 are bonded to each other with a sealing material SE in a state where a predetermined gap is formed between them. The liquid crystal layer LC is held on the inner side surrounded by the sealing material SE in the gap between the first substrate SUB1 and the second substrate SUB2. The display panel PNL includes a display area DA for displaying an image on the inner side surrounded by the seal material SE. The display area DA is composed of a plurality of pixels PX. In the illustrated example, the display area DA is formed in a quadrangular shape, but may be formed in other polygonal shapes, and may be formed in other shapes such as a circular shape or an elliptical shape.

  The first substrate SUB1 includes a gate line G, a source line S, a switching element SW, a pixel electrode PE, a common electrode CE, and the like in the display area DA. The gate line G extends, for example, along the first direction X. The source line S extends along a second direction Y that intersects the first direction X. In the illustrated example, the first direction X and the second direction Y are orthogonal to each other. Note that the gate line G may not be formed in a straight line parallel to the first direction X, and the source line S may not be formed in a straight line parallel to the second direction Y. For example, the gate line G and the source line S may be bent or partially branched.

  The switching element SW is electrically connected to the gate line G and the source line S in each pixel PX. The pixel electrode PE is electrically connected to the switching element SW in each pixel PX. The common electrode CE is provided in common for the plurality of pixels PX and is set to a common potential.

  Signal supply sources necessary for driving the display panel PNL such as the driving IC chip CP and the flexible printed circuit (FPC) substrate FL are located in the non-display area NDA outside the display area DA. In the illustrated example, the driving IC chip CP and the FPC board FL are mounted on the mounting portion MT of the first board SUB1 extending outward from the second board SUB2.

  The display panel PNL is, for example, a transmissive type having a transmissive display function for displaying an image by selectively transmitting light from a backlight unit BL described later, but is not limited thereto. . For example, the display panel PNL may be of a reflective type having a reflective display function of displaying an image by selectively reflecting light from the display surface side such as external light or auxiliary light. The display panel PNL may be a transflective type having a transmissive display function and a reflective display function.

  FIG. 2 is a plan view showing a configuration example of one pixel PX on the first substrate SUB1 shown in FIG. Note that here, as an example of the display mode, a pixel structure of a display panel PNL to which an FFS (Fringe Field Switching) mode which is one of the horizontal electric field methods is applied will be described.

The first substrate SUB1 includes gate lines G1 and G2, source lines S1 and S2, a switching element SW, a relay electrode RE, a pixel electrode PE, and the like. Here, illustration of the common electrode CE is omitted.
The gate wiring G1 and the gate wiring G2 respectively extend along the first direction X and are arranged at intervals in the second direction Y. The source wiring S1 and the source wiring S2 extend substantially along the second direction Y, and are arranged at intervals in the first direction X. The gate line G1 and the gate line G2, and the source line S1 and the source line S2 intersect each other.

  The switching element SW is located near the intersection of the gate line G1 and the source line S1, and is electrically connected to the gate line G1 and the source line S1. The switching element SW includes a semiconductor layer SC. The switching element SW in the illustrated example has a double gate structure including the gate electrodes WG1 and WG2, but is not limited to the illustrated example, and may have a single gate structure, for example. The gate electrodes WG1 and WG2 are both part of the gate wiring G1 facing the semiconductor layer SC. One end side of the semiconductor layer SC is electrically connected to the source line S1, and the other end side is electrically connected to the pixel electrode PE. The source line S1 is in contact with one end side of the semiconductor layer SC through the contact hole CH1. The relay electrode RE is located between the other end side of the semiconductor layer SC and the pixel electrode PE. The relay electrode RE is in contact with the other end side of the semiconductor layer SC through the contact hole CH2. The pixel electrode PE is in contact with the relay electrode RE through the contact hole CH3.

  The pixel electrode PE in the illustrated example includes a strip electrode (linear electrode, comb electrode) PA, a contact portion PB, and a connecting portion PC. In one example, one pixel electrode PE has two strip electrodes PA. These strip electrodes PA are arranged at intervals in the first direction X. The contact portion PB overlaps the relay electrode RE in the XY plane defined by the first direction X and the second direction Y. The connecting portion PC is located on the side close to the gate line G2 between the gate lines G1 and G2. The strip electrode PA is located between the contact part PB and the connection part PC, and is connected to the contact part PB on one end side (upper side in the drawing) and connected to the connection part PC on the other end side (lower side in the drawing). Yes. Note that the shape of the pixel electrode PE is not limited to the illustrated example. For example, the connecting portion PC may be omitted, and the number of the strip electrodes PA may not be two. However, as shown in the figure, when the pixel electrode PE is formed in a loop shape by the two strip electrodes PA, the contact portion PB, and the connecting portion PC, the width of the pixel electrode PE is increased with the increase in definition. Even if becomes smaller, the redundancy can be improved. That is, even if a disconnection occurs in a part of the pixel electrode PE, the pixel potential can be supplied to any part by a path through another part.

  Here, attention is focused on one strip electrode PA. The strip electrode PA has edges (end portions) EG on the source line S1 side and the source line S2 side, respectively. In the illustrated example, the edge EG has portions E1 to E7. The portions E1 to E7 are arranged in the second direction Y in this order. That is, the portion E1 corresponds to the first end portion located on the gate wiring G1 side in the edge EG, and the portion E7 corresponds to the second end portion located on the gate wiring G2 side in the edge EG. The parts E2 to E6 correspond to an intermediate part located between the parts E1 and E7. The portions E2 to E6 constitute bent intermediate portions where portions extending in different directions are adjacent to each other. In one example, all of the portions E1 to E7 have the same length. The shape of the strip electrode PA or the shape of the edge EG is not limited to the illustrated example, and the number of portions included in the edge EG is not limited to the illustrated example.

  Here, the second direction Y orthogonal to the gate wirings G1 and G2 is set as a reference direction. The portions E3 and E5 extend in the direction D1 of the first angle θ1 with respect to the second direction Y. The portions E2, E4, E6 extend in the direction D2 of the second angle θ2 with respect to the second direction Y. The directions D1 and D2 are directions that intersect the second direction Y at an acute angle in a counterclockwise direction. The first angle θ1 is different from the second angle θ2. In the illustrated example, the portions E1 and E7 extend in the direction D1 of the first angle θ1 as in the portion E3. In the present specification, the first direction X, the second direction Y, the direction D1 of the first angle θ1, the direction D2 of the second angle θ2, and the like are not limited to the directions of the arrows in the figure. The direction opposite 180 degrees is also included.

Hereinafter, a preferable relationship between the first angle θ1 and the second angle θ2 will be described. First, it is desirable to satisfy the following relationship.
5 ° ≦ θ1 ≦ 30 °, 0 ° ≦ θ2 ≦ 20 °, θ1> θ2 ≧ 0
When a negative liquid crystal material having negative dielectric anisotropy is used as the liquid crystal layer LC, it is desirable that the first angle θ1 and the second angle θ2 satisfy the following relationship.
10 ° ≦ θ1 ≦ 30 °, 0 ° ≦ θ2 ≦ 20 °, θ1> θ2 ≧ 0
In that case, it is desirable that the following relationship is further satisfied in consideration of the transmittance per pixel described later.
θ1-θ2 ≧ 20 °
In addition, when considering the liquid crystal response speed described later, it is further desirable to satisfy the following relationship.
θ1-θ2 ≧ 10 °
Further, when a positive liquid crystal material having positive dielectric anisotropy is used as the liquid crystal layer LC, it is desirable that the first angle θ1 and the second angle θ2 satisfy the following relationship.
5 ° ≦ θ1 ≦ 20 °, 0 ° ≦ θ2 ≦ 10 °, θ1> θ2 ≧ 0
In that case, it is desirable that the following relationship is further satisfied in consideration of the transmittance per pixel described later.
θ1-θ2 ≧ 5 °
In the illustrated example, the case where the edge EG has straight portions E1 to E7 has been described. However, the edge EG may be a curved line. When the edge EG is a curved line, a tangent at an intermediate point between adjacent vertices or a tangent at an inflection point of the curve may extend in the direction D1 or the direction D2.

  Although omitted in FIG. 2, a region overlapping with the gate line G1 and the contact part PB and a region between the connecting part PC and the gate line G2 overlap with the light shielding layer of the second substrate.

  FIG. 3 is a cross-sectional view of the first substrate SUB1 along the line AB in FIG. In the following description, the direction from the first substrate SUB1 toward the second substrate SUB2 is defined as upward (or simply upward), and the direction from the second substrate SUB2 toward the first substrate SUB1 is defined as downward (or simply downward).

  The first substrate SUB1 includes a first insulating substrate 10, a first insulating film 11, a second insulating film 12, a third insulating film 13, a fourth insulating film 14, a fifth insulating film 15, a switching element SW, a relay electrode RE, A pixel electrode PE, a common electrode CE, a first alignment film AL1, and the like are provided. In the illustrated example, the switching element SW is a top gate type, but may be a bottom gate type.

  The first insulating substrate 10 is a light transmissive substrate such as a glass substrate or a resin substrate. The first insulating film 11 is located on the first insulating substrate 10. The semiconductor layer SC of the switching element SW is located on the first insulating film 11. The semiconductor layer SC is formed of, for example, polycrystalline silicon, but may be formed of amorphous silicon, an oxide semiconductor, or the like.

  The second insulating film 12 is located on the first insulating film 11 and the semiconductor layer SC. Gate electrodes WG1 and WG2, which are part of the gate wiring G1, are located on the second insulating film 12 and face the semiconductor layer SC. The third insulating film 13 is located on the gate electrodes WG 1 and WG 2 and the second insulating film 12. The source line S1 and the relay electrode RE are located on the third insulating film 13. The source line S1 is in contact with the semiconductor layer SC through a contact hole CH1 that penetrates the second insulating film 12 and the third insulating film 13. The relay electrode RE is in contact with the semiconductor layer SC through a contact hole CH2 that penetrates the second insulating film 12 and the third insulating film 13. The fourth insulating film 14 is located on the third insulating film 13, the source wiring S1, and the relay electrode RE.

  The common electrode CE is located on the fourth insulating film 14. The common electrode CE is opposed to the gate line G1, the source line S1, and the switching element SW. The common electrode CE is also opposed to the gate line G2, the source line S2, and the like shown in FIG. The common electrode CE has an opening AP at a position facing the relay electrode RE.

  The fifth insulating film 15 is located on the fourth insulating film 14 and the common electrode CE. The first insulating film 11, the second insulating film 12, the third insulating film 13, and the fifth insulating film 15 are formed of an inorganic material such as silicon nitride (SiN) or silicon oxide (SiO), for example. Yes. The fourth insulating film 14 is made of an organic material such as an acrylic resin.

  The pixel electrode PE is located on the fifth insulating film 15 and faces the common electrode CE. The pixel electrode PE is in contact with the relay electrode RE through a contact hole CH3 that penetrates the fourth insulating film 14 and the fifth insulating film 15. The common electrode CE and the pixel electrode PE are formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The first alignment film AL1 is located on the fifth insulating film 15 and the pixel electrode PE. The first alignment film AL1 is made of, for example, a material that exhibits horizontal alignment.

  In the illustrated example, the common electrode CE corresponds to the first electrode, the pixel electrode PE corresponds to the second electrode, and the fifth insulating film 15 corresponds to the interlayer insulating film.

FIG. 4 is a cross-sectional view of the display panel PNL along the line CD in FIG.
In the first substrate SUB1, the source lines S1 and S2 are located on the third insulating film 13 and covered with the fourth insulating film 14. The common electrode CE is located on the fourth insulating film 14 and is covered with the fifth insulating film 15. The common electrode CE extends to a position facing the source lines S1 and S2, and also extends to a position facing a gate line and a switching element (not shown). The pixel electrode PE is located on the fifth insulating film 15 and is covered with the first alignment film AL1. The pixel electrode PE is located on the inner side of the position immediately above the source wirings S1 and S2, and faces the common electrode CE. The edge EG of the pixel electrode PE is located between the common electrode CE and the liquid crystal layer LC. In the illustrated example, the edge EG is located immediately above the common electrode CE.

  The second substrate SUB2 includes a second insulating substrate 20, a light shielding layer SH, a color filter CF, an overcoat layer OC, a second alignment film AL2, and the like.

  The second insulating substrate 20 is a light transmissive substrate such as a glass substrate or a resin substrate. The light shielding layer SH is located on the side of the second insulating substrate 20 facing the first substrate SUB1. The light shielding layer SH is located immediately above the source lines S1 and S2, and is also located immediately above a gate line and a switching element (not shown). The color filter CF is opposed to the pixel electrode PE. The end of the color filter CF overlaps with the light shielding layer SH. The color filter CF is formed of, for example, a resin material colored in red, green, or blue. The color filter CF may include a white color filter or a transparent color filter. The overcoat layer OC is formed of a transparent resin material and covers the color filter CF. The second alignment film AL2 is located on the side of the overcoat layer OC that faces the first substrate SUB1. The alignment film AL2 is formed of a material exhibiting horizontal alignment. In the illustrated example, the color filter CF is provided on the second substrate SUB2, but may be provided on the first substrate SUB1.

  The first substrate SUB1 and the second substrate SUB2 as described above are arranged so that the first alignment film AL1 and the second alignment film AL2 face each other. A predetermined cell gap is formed between the first substrate SUB1 and the second substrate SUB2. The liquid crystal layer LC is sealed between the first alignment film AL1 of the first substrate SUB1 and the second alignment film AL2 of the second substrate SUB2. The liquid crystal layer LC is made of a liquid crystal material having a negative dielectric anisotropy (negative type) or a liquid crystal material having a positive dielectric anisotropy (positive type).

  The backlight unit BL is disposed on the back side of the display panel PNL. In the present embodiment, various types of backlight units BL can be applied, but description of the detailed structure thereof is omitted.

  A first optical element OD1 including a first polarizing plate PL1 is disposed on the outer surface of the first insulating substrate 10. On the outer surface of the second insulating substrate 20, the second optical element OD2 including the second polarizing plate PL2 is disposed. The first polarizing axis of the first polarizing plate PL1 and the second polarizing axis of the second polarizing plate PL2 are, for example, in a crossed Nicols positional relationship in the XY plane.

  Next, the operation of the liquid crystal display device having the above configuration will be described. First, the case where the liquid crystal layer LC is made of a negative liquid crystal material will be described with reference to FIG.

  In a state in which no voltage is applied to the liquid crystal layer LC, that is, in an off state in which an electric field is not formed between the pixel electrode PE and the common electrode CE, the liquid crystal molecules LM, as indicated by broken lines in the figure, In the XY plane, the major axis is initially oriented in a direction parallel to the first direction X. In the drawing, liquid crystal molecules LM in the vicinity of portions E3 and E4 of the edge EG are shown. Such an off time corresponds to the initial alignment state, and the alignment direction of the liquid crystal molecules LM at the off time corresponds to the initial alignment direction AL0. The initial alignment direction AL0 is a direction perpendicular to the second direction Y (reference direction). The initial alignment state is realized by aligning both the first alignment film AL1 and the second alignment film AL2 in the first direction X. About the method of alignment processing, rubbing processing may be sufficient and other methods, such as optical alignment processing, may be sufficient.

  When off, a part of the backlight light from the backlight unit BL passes through the first polarizing plate PL1 and enters the display panel PNL. The light incident on the display panel PNL is linearly polarized light orthogonal to the first polarization axis (or absorption axis) AX1 of the first polarizing plate PL1. The polarization state of linearly polarized light hardly changes when it passes through the liquid crystal layer LC in the off state. For this reason, the linearly polarized light transmitted through the display panel PNL is absorbed by the second polarizing plate PL2 having a crossed Nicols positional relationship with respect to the first polarizing plate PL1 (black display).

  On the other hand, in a state where a voltage is applied to the liquid crystal layer LC, that is, when an electric field is formed between the pixel electrode PE and the common electrode CE, the liquid crystal molecules LM are as shown by a solid line in the drawing. The orientation is different from the initial orientation direction AL0. In the figure, the arrow indicates the rotation direction of the liquid crystal molecules LM with respect to the initial alignment direction AL0. That is, the electric field formed at the time of on is formed along the edge EG of the pixel electrode PE in the XY plane, and the direction of the electric field is substantially perpendicular to the edge EG. The alignment state of the liquid crystal molecules LM changes under the influence of the formed electric field. In the case of a negative type liquid crystal material, the liquid crystal molecules LM are aligned so that the major axis thereof is in a direction substantially perpendicular to the electric field.

  In the present embodiment, the liquid crystal molecules form a region rotated in the same direction with respect to the initial direction AL0 in the region along each part of the edge EG. In the illustrated example, the liquid crystal molecules LM in the vicinity of the portions E3 and E4 rotate in the clockwise direction with respect to the initial alignment direction AL0 in the XY plane, and the major axis thereof is substantially the same as each portion of the edge EG. Oriented to face parallel directions. Similarly, in the region along the other part of the edge EG, the liquid crystal molecule LM forms a region rotated in the clockwise direction.

  The portion E3 extends in a direction different from that of the portion E4. For this reason, the liquid crystal molecules LM near the portion E3 may be aligned in a different direction from the liquid crystal molecules LM near the portion E4. That is, since the portion E3 extends in the direction D1, the liquid crystal molecules LM in the vicinity of the portion E3 are aligned so that the major axis thereof is in a direction substantially parallel to the direction D1. Further, since the portion E4 extends in the direction D2, the liquid crystal molecules LM in the vicinity of the portion E4 are aligned so that the major axis thereof is in a direction substantially parallel to the direction D2. However, as described above, the difference between the first angle θ1 and the second angle θ2 is as small as 20 ° or less, and the liquid crystal molecules near the portions E3 and E4 rotate in the same direction. It can be said that it forms.

  The angle θ11 formed by the initial alignment direction AL0 and the direction D1 is smaller than the angle θ12 formed by the initial alignment direction AL0 and the direction D2. For this reason, the energy necessary for the liquid crystal molecules LM near the portion E3 to rotate is smaller than the energy necessary for the liquid crystal molecules LM near the portion E4 to rotate. Therefore, the liquid crystal molecules LM near the portion E3 are more likely to rotate at a higher speed than the liquid crystal molecules LM near the portion E4.

  In such an on state, the linearly polarized light incident on the display panel PNL changes according to the alignment state of the liquid crystal molecules LM when the polarization state passes through the liquid crystal layer LC. For this reason, at the time of ON, at least part of the light that has passed through the liquid crystal layer LC is transmitted through the second polarizing plate PL2 (white display).

  Next, the operation of the liquid crystal display device having the above configuration will be described with reference to FIG. 6 in the case where the liquid crystal layer LC is composed of a positive liquid crystal material.

  At the off time, the liquid crystal molecules LM are initially aligned in the direction parallel to the second direction Y in the XY plane, as indicated by a broken line in the drawing. The initial alignment direction AL0 is a direction parallel to the second direction Y (reference direction). In such an off state, as described with reference to FIG. 5, linearly polarized light incident on the display panel PNL hardly changes when the polarization state passes through the liquid crystal layer LC in the off state. The first polarizing plate PL1 is absorbed by the second polarizing plate PL2 having a crossed Nicol positional relationship (black display).

  At the on time, the liquid crystal molecules LM are aligned in a direction different from the initial alignment direction AL0, as indicated by a solid line in the figure. In the case of a positive type liquid crystal material, the liquid crystal molecules LM are aligned so that the major axis thereof is in a direction substantially parallel to the electric field. In the illustrated example, the liquid crystal molecules LM in the vicinity of the portions E3 and E4 rotate in the clockwise direction with respect to the initial alignment direction AL0 in the XY plane, and the major axis thereof is substantially the same as each portion of the edge EG. Oriented so as to face the vertical direction. Similarly, in the region along the other part of the edge EG, the liquid crystal molecule LM forms a region rotated in the clockwise direction.

  In such an on state, the linearly polarized light incident on the display panel PNL changes according to the alignment state of the liquid crystal molecules LM when the polarization state passes through the liquid crystal layer LC, and at least a part of the light is second The light passes through the polarizing plate PL2 (white display).

  According to the present embodiment, the edge EG of the pixel electrode PE has a bent intermediate portion in the space between the contact portion PB and the connecting portion PC. For this reason, the edge length can be increased as compared with the case where the edge EG is formed in a straight line. Moreover, when an electric field is formed along the edge EG of the pixel electrode PE, the liquid crystal molecules LM form a region rotated in the same direction with respect to the initial alignment direction, and substantially form a single domain. For this reason, it is possible to improve the transmittance per pixel as compared with the case where the edge EG is formed in a straight line.

  Further, in the region along the edge EG, the region where the liquid crystal molecules LM rotating in the opposite directions do not antagonize does not occur, and thus it is possible to suppress the occurrence of dark lines due to the propagation of such a region. Become. Further, since the rotation direction of the liquid crystal molecules LM at the time of ON is uniquely determined, the liquid crystal molecules LM rotate in a predetermined direction to form a desired alignment state even if a stress pressed from the outside is applied. And display unevenness can be suppressed.

  Further, according to the present embodiment, the edge EG of the pixel electrode PE includes a portion that intersects the initial alignment direction AL0 of the liquid crystal molecules LM at a relatively large angle. The electric field generated in such a portion can rotate the liquid crystal molecules LM at high speed. For this reason, it is possible to increase the liquid crystal response speed required from the start of voltage application for forming an electric field to the stabilization of the alignment state of the liquid crystal molecules LM. In the example shown in FIG. 5, the liquid crystal molecules LM near the portion E3 in the edge EG are more likely to rotate at a higher speed than the liquid crystal molecules LM near the portion E4. Further, the rotation speed of the liquid crystal molecules LM in the vicinity of the portion E4 is accelerated by the influence of the liquid crystal molecules LM in the vicinity of the adjacent portion E3. For this reason, it is possible to increase the liquid crystal response speed over substantially the entire region along the edge EG.

  By the way, the film thickness of the alignment film affects the sensitivity of the electric field acting on the liquid crystal molecules LM. That is, in the region where the alignment film is thick, the electric field is less likely to act on the liquid crystal molecules LM than in the region where the film thickness is thin. For this reason, when the film thickness of the alignment film is not uniform within one pixel, the alignment state of the liquid crystal molecules LM differs between the thick film area and the thin film area, which may cause deterioration in display quality.

  According to the present embodiment, since the edge EG of the pixel electrode PE is bent, the electric field acting on the liquid crystal molecules LM when turned on is generated along different directions in each bent portion. Each generated electric field acts to align the liquid crystal molecules LM in slightly different directions. For this reason, even if the film thickness of the alignment film becomes non-uniform within one pixel, regions having different alignment states are mixed along the edges EG bent at a plurality of locations, and are spatially dispersed. As a result, the deterioration in display quality due to the difference in the orientation state becomes difficult to be visually recognized.

  As described above, according to the present embodiment, display quality can be improved.

  Next, the relationship between the first angle θ1 and the second angle θ2 and the VT characteristic will be described. Here, the VT characteristic indicates the relationship of the transmittance of the display panel PNL to the voltage (V) applied to the liquid crystal layer LC.

  FIG. 7 is a diagram showing a simulation result of VT characteristics when a negative liquid crystal material is used. In (A) to (D) in the figure, the horizontal axis represents the applied voltage, and the vertical axis represents the transmittance.

  (A) in the figure shows VT characteristics when the pixel electrode PE has a linear edge EG. The first angle θ1 and the second angle θ2 are both 15 °. The transmittance when the applied voltage is 4.5V is 0.333, and the transmittance when the applied voltage is 5V is 0.351.

Each of (B) to (D) in the figure shows VT characteristics when the pixel electrode PE has a bent edge EG.
(B) corresponds to the case where the first angle θ1 is 20 ° and the second angle θ2 is 10 °. The transmittance when the applied voltage is 4.5V is 0.334, and the transmittance when the applied voltage is 5V is 0.353.
(C) corresponds to the case where the first angle θ1 is 30 ° and the second angle θ2 is 0 °. The transmittance when the applied voltage is 4.5V is 0.342, and the transmittance when the applied voltage is 5V is 0.360.
(D) corresponds to the case where the first angle θ1 is 25 ° and the second angle θ2 is 5 °. The transmittance when the applied voltage is 4.5V is 0.342, and the transmittance when the applied voltage is 5V is 0.359.

According to the above simulation results, when the pixel electrode PE has the bent edge EG (B) to (D), compared with the case where the pixel electrode PE has the linear edge EG (A), It was also confirmed that the transmittance can be improved. In particular, as shown in (C) and (D), when the difference (θ1−θ2) between the first angle θ1 and the second angle θ2 is 20 ° or more, the transmission is compared with (A). It was confirmed that the rate could be increased by about 2%.
When a positive liquid crystal is used, the initial alignment direction of liquid crystal molecules is AL0 as shown in FIG. The initial alignment direction AL0 is a direction orthogonal to the gate wiring. When the edge EG of the pixel electrode is bent with respect to the initial alignment direction AL0, for example, when the first angle θ1 is 10 ° and the second angle θ2 is 0 °, the edge EG is extended uniformly at 5 ° without bending the edge. The transmittance was improved by 3.6% compared to that of the case. An improvement in transmittance was also observed when the first angle θ1 was bent at 8 ° and the second angle θ2 was bent at 2 °. That is, when positive liquid crystal is used, it is desirable to bend the edges in the ranges of 5 ° ≦ θ1 ≦ 20 °, 0 ° ≦ θ2 ≦ 10 °, and θ1> θ2 ≧ 0. Further, it is preferable that θ1−θ2 ≧ 5 ° is satisfied.

  Next, the relationship between the first angle θ1 and the second angle θ2 and the liquid crystal response time will be described. The liquid crystal response time here means that the transmittance reaches 10% to 90% when the maximum transmittance obtained when a voltage corresponding to a specific gradation is applied to the liquid crystal layer LC is 100%. It is defined as the time required to do.

  FIG. 8 is a diagram showing a simulation result of the liquid crystal response time when a negative liquid crystal material is used. In the figure, the horizontal axis represents time (μs), and the vertical axis represents transmittance. Here, the liquid crystal response time when a voltage (2.5 V) corresponding to the intermediate gradation was applied to the liquid crystal layer LC was calculated. (A) through (D) in the figure correspond to the respective cases (A) through (D) described with reference to FIG.

  The liquid crystal response time of (A) was 49 μs. The liquid crystal response time of (B) was 42 μs. The liquid crystal response time of (C) was 42 μs. The liquid crystal response time of (D) was 46 μs. According to the above simulation results, when the pixel electrode PE has the bent edge EG (B) to (D), compared with the case where the pixel electrode PE has the linear edge EG (A), It was also confirmed that the liquid crystal response time can be shortened. In particular, as shown in (B) to (D), when the difference (θ1−θ2) between the first angle θ1 and the second angle θ2 is 10 ° or more, the liquid crystal is compared with (A). It was confirmed that the response time can be shortened by about 16% and the liquid crystal response speed can be increased.

  Next, another configuration example of this embodiment will be described. Hereinafter, main differences will be described, and the same components as those in the above-described example will be denoted by the same reference numerals, and detailed description thereof will be omitted.

  FIG. 9 is a plan view showing another configuration example of one pixel PX on the first substrate SUB1 shown in FIG. The configuration example shown in FIG. 9 is different from the configuration example shown in FIG. 2 in the shape of the strip electrode PA or its edge EG. More specifically, in the strip electrode PA, the portion connected to the contact portion PB is longer than the portion connected to the connecting portion PC. Focusing on the edge EG, in the illustrated example, the edge EG has portions E1 to E5. The parts E1 to E5 are arranged in the second direction Y in this order. The part E1 is connected to the contact part PB, and the part E5 is connected to the connecting part PC. The parts E2 to E4 correspond to an intermediate part located between the parts E1 and E5. The portions E2 to E4 constitute bent intermediate portions where portions extending in different directions are adjacent to each other. In the illustrated example, the portions E1, E3, and E5 extend in the direction D1. The portions E2 and E4 extend in the direction D2. The length of the part E1 is longer than the other parts E2 to E5.

  Also in such a configuration example, the same effect as the above configuration example can be obtained. In addition, the part E1 connected to the contact part PB is longer than the parts E2 to E5 and extends in a direction intersecting with the second direction Y (reference direction) at a relatively large angle. For this reason, in the XY plane, even when the alignment film has a non-uniform thickness in the region overlapping the contact portion PB, particularly in the periphery of the region overlapping the contact hole CH3, the edge EG has a portion E1. The along electric field acts on the liquid crystal molecules LM over a relatively long distance, and the liquid crystal molecules LM can be aligned in a desired direction. Therefore, it is possible to suppress a decrease in display quality.

  FIG. 10 is a plan view showing another configuration example of one pixel PX on the first substrate SUB1 shown in FIG. In the configuration example shown in FIG. 10, the pixel electrode PE is formed in a flat plate shape having no slit, and the common electrode CE is higher than the pixel electrode PE, compared to the configuration example shown in FIG. 2. It is different in that it has a slit SL. Here, the main parts necessary for the description are shown, and illustration of switching elements, relay electrodes, and the like is omitted.

  The pixel electrode PE is located between the source lines S1 and S2, and is formed in an island shape. The common electrode CE is located on the upper layer side than the gate line G1, the source lines S1 and S2, and the pixel electrode PE. Further, the common electrode CE has a slit SL facing the pixel electrode PE. In the illustrated example, the common electrode CE corresponds to the second electrode, and the pixel electrode PE corresponds to the first electrode.

  The edge EG that defines the slit SL is configured similarly to the edge EG of the strip electrode PA shown in FIG. In the illustrated example, the edge EG has portions E1 to E7 arranged in order in the second direction Y. The parts E2 to E6 correspond to an intermediate part located between the parts E1 and E7. The portions E2 to E6 constitute bent intermediate portions where portions extending in different directions are adjacent to each other. The portions E1, E3, E5, E7 extend in the direction D1. The portions E2, E4, E6 extend in the direction D2. The angle between the directions D1 and D2 and the second direction Y is as described with reference to FIG.

  The shape of the slit SL or the shape of the edge EG is not limited to the illustrated example, and the number of portions included in the edge EG is not limited to the illustrated example. For example, the alignment of the liquid crystal tends to be unstable in the strip electrode in the vicinity of the connection portion such as the contact portion PB and the connecting portion PC. Therefore, the angles of the portions E1 and E7 (E5 in the embodiment of FIG. 9) can be different from the angles of the portions E3 and E5 (the portion E3 in the embodiment of FIG. 9).

  Also in such a configuration example, the same effect as the above configuration example can be obtained.

  FIG. 11 is a plan view showing another configuration example of one pixel PX on the first substrate SUB1 shown in FIG. The configuration example shown in FIG. 11 is different from the configuration example shown in FIG. 2 in the shape of the strip electrode PA or its edge EG. More specifically, in the strip electrode PA of the pixel electrode PE, the edge EG has portions E1 to E10 arranged in order in the second direction Y.

  The parts E2 to E4 correspond to an intermediate part located between the parts E1 and E5. The portions E2 to E4 constitute bent intermediate portions where portions extending in different directions are adjacent to each other. The parts E1, E3, E5 extend in the direction D1. The portions E2 and E4 extend in the direction D2. The angle between the directions D1 and D2 and the second direction Y is as described with reference to FIG.

  The parts E7 to E9 correspond to an intermediate part located between the part E6 and the part E10. The portions E7 to E9 constitute a bent intermediate portion in which portions extending in different directions are adjacent to each other. The portions E6, E8, and E10 extend in the direction D3 of the third angle θ3 with respect to the second direction Y. The portions E7 and E9 extend in the direction D4 of the fourth angle θ4 with respect to the second direction Y. The directions D3 and D4 are directions that intersect the second direction Y at an acute angle in the clockwise direction. The third angle θ3 is different from the fourth angle θ4. In one example, the third angle θ3 is substantially the same as the first angle θ1, and the fourth angle θ4 is substantially the same as the second angle θ2. However, the present invention is not limited to this example.

  In the region of the parts E1 to E5 close to the contact part PB, the liquid crystal molecules LM form a region rotated in the same direction when turned on. Also in the regions of the portions E6 to E10 adjacent to the connecting portion PC, the liquid crystal molecules LM form a region rotated in the same direction when turned on. However, the rotation direction of the liquid crystal molecules LM differs between the regions E1 to E5 and the regions E6 to E10.

  For example, when a positive type liquid crystal material is applied, the liquid crystal molecules LM are initially aligned in the second direction Y as indicated by the dotted line in the drawing. In the region of the portions E1 to E5, the liquid crystal molecules LM rotate clockwise as shown by the solid line, and substantially form a single domain. In the region of the portions E6 to E10, the liquid crystal molecules LM rotate counterclockwise as shown by the solid line, and substantially form a single domain. When a negative type liquid crystal material is applied, the liquid crystal molecules LM are initially aligned in the first direction X.

  According to such a configuration example, in addition to obtaining the same effect as the above configuration example, it is possible to form two domains per pixel. Therefore, the viewing angle can be optically compensated in a plurality of directions, and a wide viewing angle can be achieved. In FIG. 11, the belt-like electrode is formed in a convex shape on the right side in the drawing, but may be formed in a convex shape on the left side. In this case, the directions D1 to D4 are symmetric with respect to the second direction Y.

  As described above, according to this embodiment, a liquid crystal display device capable of improving display quality can be provided.

  In addition, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

PNL ... display panel SUB1 ... first substrate SUB2 ... second substrate LC ... liquid crystal layer G ... gate wiring S ... source wiring SW ... switching element PE ... pixel electrode CE ... common electrode
EG ... Edge E1-E10 ... Edge part

Claims (11)

A first wiring; a second wiring spaced apart from the first wiring; a first electrode; a second electrode facing the first electrode; and an interlayer positioned between the first electrode and the second electrode A first substrate comprising an insulating film;
A second substrate facing the first substrate;
A liquid crystal layer including liquid crystal molecules held between the first substrate and the second substrate,
The second electrode has an edge located between the first electrode and the liquid crystal layer;
The edge includes a first portion located on the first wiring side, a second portion located on the second wiring side, and a bent middle portion located between the first portion and the second portion. Have
The liquid crystal display device, wherein the liquid crystal molecules form a region rotated in the same direction by an electric field between the first electrode and the second electrode in a region between the first part and the second part.   The intermediate portion extends in a first angle direction with respect to a reference direction perpendicular to the first wiring, and in a second angle direction different from the first angle with respect to the reference direction. The liquid crystal display device according to claim 1, further comprising an extended fourth portion. The liquid crystal layer is a negative liquid crystal layer,
When the first angle is θ1 and the second angle is θ2,
10 ° ≦ θ1 ≦ 30 °, 0 ° ≦ θ2 ≦ 20 °, θ1> θ2 ≧ 0
The liquid crystal display device according to claim 2, satisfying the relationship: θ1-θ2 ≧ 20 °
The liquid crystal display device according to claim 3, satisfying the relationship: θ1-θ2 ≧ 10 °
The liquid crystal display device according to claim 3, satisfying the relationship: The liquid crystal layer is a positive liquid crystal layer,
When the first angle is θ1 and the second angle is θ2,
5 ° ≦ θ1 ≦ 20 °, 0 ° ≦ θ2 ≦ 10 °, θ1> θ2 ≧ 0
The liquid crystal display device according to claim 2, satisfying the relationship: θ1-θ2 ≧ 5 °
The liquid crystal display device according to claim 6, satisfying the relationship:   The liquid crystal display device according to claim 3, wherein the first portion and the second portion extend in the direction of the first angle. A switching element electrically connected to the first wiring;
9. The liquid crystal display device according to claim 1, wherein the second electrode includes a strip electrode that is electrically connected to the switching element and includes the edge. A switching element electrically connected to the first wiring;
The first electrode is electrically connected to the switching element;
The liquid crystal display device according to claim 1, wherein the second electrode has a slit defined by the edge. The edge further includes a fifth portion located on the second wiring side with respect to the second portion,
The liquid crystal molecule forms a region rotated in a direction different from a region between the first portion and the second portion in a region between the second portion and the fifth portion. 11. The liquid crystal display device according to any one of 1 to 10.

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